Zinc furnace



C. HAHN ZINC FURNACE May 9, 1933.

Filed May 14, 1931 4 Sheets-Sheet 1 www@ May 9, 1933. HAHN @,@saz

ZINC FURNACE Filed May 14, 1951 4 SheetS-Sheet 2 f m, Y if@ alf May 9, 1933. Q HAHN 1,908,632

MNC FURNACE' Filed May 14, 1931 4 sheets-sheet 3 May 9, 1933. C. HAHN 1598,632

ZINC FURNACE Filed May 14, 1931 4 Sheets-Sheet 4 Patented May 9, 1933 UNITED STATES PATENT OFFICE CONRAD HAHN, 0F ESSEN, GERMANY, ASSIGNOR, BY MESNE ASSIGNMENTS, T0 THE KGPPERS COMPANY OF DELAWARE, 0F PITTSBURGH, PENNSYLVANIA, A. CORPORA- TION F DELAWARE ZINC FUR/NACE Application led May 14, 1931, SerialvNo. 537,319, and in Germany May 9, 1930.

My invention relates to the recovery of zinc from zincA oxide-bearing substances which contain lead and is concerned with certain improvements in the furnaces used for carrying out this recovery of zinc, so that the lead is separated from the zinc more eHectively than before.

Generally, zinc is recovered from zinc oxide-containing ores by heating these ores together with carbon preferably in a vertical shaft furnace. Theogases thereby evolved, which for the greater part consist of zinc vapours, lead vapour and carbonio oxides, are preferably withdrawn at the top of the furnace and passed to a cooler outside the furnace, where the metallic vapours condense to liquid metal. In these zinc recovery furnaces, in order to prevent the liberated lead from passing into the cooler at the same time as the zinc, it has been customary hitherto to allow these distillation gases to sweep over a layer of cold distillation material before passing out of the shaft furnace into the cooler. This distillation material then absorbs a portion of the sensible heat of the gases and the latter are so cooled that the lead is deposited whilst the zinc still remains in the form of vapour. In actual practice however, it has been found that this arrangement can only be used for ores which are rich in zinc. lf on the other hand, ores poor in zinc are treated, the quantity of the' ases and metallic vapours evolved in the sha t furnace during the reducing is so small that they are insuiicient to preheat the cold distillation prod. uct to such a temperature at which the lead will settle but the zinc vapours will not condense. On the contrary, the gases cool more rapidly and the zinc vapors also begin to condense, so that the efficiency of the reduction furnace suffers appreciably.

The present invention now aims in the vfirst place at an improvement in the recovery of zinc from lead-bearing oxidiferous ores in a gas-fired shaft furnace. According to the process, the charge under distillation is maintained at the temperature just essential for the condensation of the lead, in the top portion of the shaft furnace, independent of the quantity of gas evolved in the bottom portion of the shaft.` The improvement consists in this, that the walls of the distillation retorts are externally heated from the bottom discharge opening for the residue of distillation up to the distillate gas offtake opening at the'upper end of the retort. The heating is graduated according to the height however, in such a way that in the top portion n'ear the dis# tillate gas discharge opening, the heating walls are kept at a temperature at which the material in the upper part of the retort will be at about 950o so that lead vapours con# dense, but the zinc vapours do not, whereas in the lower portion of the -retorts, the heating walls are kept at such a heat as to produce the temperature of labout 1350?-in the charge necessary for releasing the metals.

The invention also relates to a zinc distillation furnace which comprises one or more vertical distillation retortsfor heating the ore and carbon mixture, the walls of these retorts being provided throughout their entire length with vertical heating passages or combustion lues. In the top section of the vertical heating passages, at the level of the limit of the condensation and reduction zone,

a horizontal partition wall provided with adjustable openings is arranged. Underneath this partition the heating passages are heated by direct fiames, whereas the heating passages above this partition are traversed by a portion of the hot combustion gases evolved n the bottom section of the vertical heating ues.

Further, the invention is concerned with` the arranging of gas and air passages in the horizontal partition wall and at the bottom of the vertical heating flues, so that the bottom sections of the vertical heating passages are alternately fired downwards from above'l and upwards from below.

Finally the invention has for its object the arranging of gas and air jets at the top of the horizontal partition wall in order that the top sections of the heating passages may also be heated by flames.

Further objects of the invention relate to the provision of dampers for the openings and at the combustion points of the partition wall in order that the top sections of the heating passages may be regulated.

The invention will be better understood by referring to the accompanying drawings, which show a preferred embodiment of the plant for carrying out the process. This is onl by way of example however and it is un erstood that the arrangement is capable of modiiication without thereby departing from the spirit of the invention.

`Referring to the drawings,

Fig. 1 represents a -vertical section of a complete arrangement for recovering zinc from lead-bearing oxidiferous ores according to the invention.

Fig. 2 is a vertical section through the 4heating wallsfand regenerators drawn to a larger scale.

Fig. 3 is a vertical section through the reduction retorts or chambers.

Fig. 4 shows a vertical section through the Vreduction retorts and the heating walls longitudinally of the row thereof.

Fig. 5 is a horizontal sectional view taken on the line 4-4 of Fig. 2;

In the arrangement shown inthe drawings, the oxidiferous zinc ore is conveyed, for example by means of a bucket elevator, into the storage bunker 1 arranged in the top of the furnace structure. The outlet 4 of this bunker is provided with a movable connecting pipe 3, which may be moved downwards by means of a hand lever 2. Underneath the bunker outlet there is arranged the charging opening 5 of an externally heated continuous vertical retort 6 of approximate rectangular cross-section. The charging opening 5 may be closed by means of a cover 56 which can be pushed over the charging opening 5 by means of a hand lever 57. Adjoining the bottom of the reduction retort there is arranged a frame type cooler 7 of cast iron or the like. At the bottom opening of the latter there is the usual delivery device 8 which passes into a discharge hopper 9. The zinc ore and carbon mixture is charged into the retort through the opening 5 and the residue of distillation is continually extracted or drawn off at the bottom part thereof, through the quenching or cooling device 7 into the continuous extractor cylinder 8 and the hopper 9. In the measure that material is withdrawn from the retort at the bottom, new material is charged into the retort at the top from the bunker 1 and thus there is a continuous'gradual descent of the material through the retort chambers so that an unfavorable accumulation of lead does not occur in the top of the retort chambers.

The lead is condensed from the zinc vapors in the upper part of the retort, and the condensed lead passes downwardly with the charge and also flows down the walls of the retort past the hot zone to the discharge de- Vice 9. It -is not revolatilized in passing the hot zone because the retort is not heated to the boilin point of lead, i. e. 1525 C. but is heater? to a lower temperature b ut high enough to volatilize zinc at its boiling point, i. e., 918 C.

In the lower portion of the externally heated retort 6, the zinc ore and carbon mixture is brought to such a temperature, that the metal oxides are reduced. This produces carbonio oxide gases and metal vapours. The gases and vapours evolved rise in the retort 6 up through the charge and leave the retort through an opening 11, which is provided at the top of the retort laterally of the charging shaft and which is connected to a condenser 13, through a heat-insulated passage 12. The metallic vapours deposit themselves in the condenser 13, which is provided with a baile surface 14. The metal accumulating in the condenser, is continuously drawn olf through the opening 15 and passes into the conveyer vessel 16, which is transportably arranged on a platform 67 of the furnace structure, in front of the condenser.

The non-condensing portions of the gases and vapours passing into the condenser .13, leave the condenser through the pipe line 17 and pass to a collecting main 18 from whence the combustible components are delivered by conduit 48 to the main 48 and thence tothe burners for heating the retorts.

The heating of the zinc ore reduction furnace will be seen from drawings 2 to 4. According to Fig. 4 several reduction retorts 6 are arranged alongside each other in a battery according to the invention. Every retort has a special charging opening 5. The heating walls 19 separating the reduction ret-Orts from each other form the sides of the retort chambers and comprise Vertical heating lues 20. The heating walls 19 are heated by these heating fiues 20 from gases which are burnt inside the fiues downwards from above and upwards from below alternately, and then removed therefrom at the top or bottom. T he combustible gases for heating the furnace are delivered to the heating fiues 20 from a main 48 through a horizontal conduit 25 which has a gas inlet jet or port 26 in each heating flue 20. The heating gases for downwardly heating the passages are however delivered to a conduit 25 with jets 26 which is arranged at the underside 'of a partition wall provided in the top section of the heating passages.

The air for burning the heating gases is supplied to the heating lues from below through a passage 21, which is accessible for control purposes through a sight hole 22. At 23, the passage 21 has an opening which leads to the distributing flue 24. The clear crosssection of the opening 23 may be varied by damper bricks 23, which are adjusted by Hue 25.

-to the heating iues 20, through openings 31.

The clear cross-section of the openings 31 may be varied by dampers 53 which may be oper-4 ated by means of operating rods inserted from outside through a Wall opening 54 of the passage 30.

Pre-heating the combustion air for the battery according to the invention is carried out by regenerators 32 and 33 which are `heated from the hot waste gases coming from the heating ues 20. As usual, the regenerators are lined with refractory bricks 39, which serve to store the heat ,from the waste gases and transfer this heat to the cold combustion air in alternation. The regenerators 32 and 33 are arranged in the furnace block above each other and laterally of the reduction retorts. The top regenerator is connected through the opening 40 to the upper horizontal air flue 30. The bottom regenerator 32 is connected at the top tothe bottom air inlet passage 21 through a vertical conduit 41. Lower passages 34 and 35 are provided in the bottom part of the regenerators. Outside the furnace block, these are connected by the pipe lines 36 to an elbow piece 37 of usual type. As is customary, this elbow piece is provided with an air door 38 which is .opened at times and allows the entry of combustion air into the pipe line 36 and thence to the regenerators 32 and 33.

Further, a pipe line 43 leading to the waste gas collecting flue 42 is connected to the elbow piece 37 and, by suitable arrangements inside the elbow piece, is alternately connected to the pipe 36 when the air-inlet valve door 38 is closed, and is closed to the pipe 36 when the door 38 is open. The air and exhaust gas valves for regenerator 32 operate in alternation with the similar valves for the regenerator 33.

As already mentioned, the fines 20 are alternately heated from above and from below. lf for instance the heating filles are heated from above, gas is passed into the upper gas Further the elbow piece 37 is so set that air is drawn into the previously heated regenerator 33. The air is preheated in this regenerator. Then it passes into the Y upper air distributing conduit 36 and from there through the jetsr31 into the heating flue,

where it is brought into contact with the gasA issuing from the jets 26 to give rise to flame formation.

The waste gases traverse the heating flues in a downward direction when the heating is from above. They pass through the openings 29 over into the bottom distributing conduit 24, passing from here through the opening 23 intothe bottom passage 21 and.-

then into the verticalue 41, finally traversing the regenerator 32 whose brickwork they heat up. When the waste gases lhave y given up their heat, they pass over at the bottom of the regenerator 32 into the passage 34, then traveling kthrough the pipe line 36 over the vsuitably set' elbow piece 37 into the waste heat flue 42 and thence to the chimney, (not shown). If required in order to obtain suiiicient draught, a fan may also be-inserted in the pipes leading to the chimney. ,i

The section 44 of the heating lines 2() situated above the partition walls 28 is soheated inthe zinc distillation furnace accordingto the invention, that the heating wall '19 assumes such a temperature in the upper part,

that the lead .vapours which are liberated along with the zinc from the zine ore just condense, Ybut the zinc vapours do not. Hence in the top part of the reduction retorts 6 there is brought about a separation of the lead vapours from the zinc vapours. Consequently the metal vapours which'escape through the opening 11, consist practically of pure zinc.

Preferably the upper heating flue sections 44 are heated by passing a portion of the hot waste gases into the upper heating flues- 44 from the bottom heating flues 20 before the gases are drawn into the regenerator 33. For this purpose there are provided in the horizontal partition walls 28 vertical passages 45 which connect the bottom heating flues 20 and the top heating lues 44 to each other. The clear crosssection of the passages 45 of the partition wall 28 may be varied from above by means of damper bricks similar to the bricks 47.

Openings 46 controlled by dampers 47 are also provided in the horizontal partition wall 28 between the horizontal fines 30 and the heating lues 44. When the top regenerator 33 is changed over to waste heat, the waste gases drawn into the heating Hue 44 may be led away through these openings. The openings 31 and 46 and the passages 45 must be so regulated that a difference of draught suiiicient to draw in the hot Waste gases through the section 4'4 is present between the passages 45 and the openings 31.

rlhe direction of combustion is changed about every thirty minutes, since that period has been found best for high heat eiiiciency of the regenerators. When the heating ilues are fired downwards from above, in the above described method of heating the lues 44 are traversed not by hot waste gases but only by the hot preheated combustion air.

During downiiow combustion such limited heating of the section 44 may also be effected by a special flame. For this purpose, the horizontal partition wall 28 is provided at the top also with a gas conduit 49 into which the gas is passed when thefgas conduitA is also in service. In this case the waste gases of the flame produced during the combustion ot the gas emerging from the gas conduit 49 are drawn ofi through thepassages 45 into the bottom heating flue 20, whence the .gases are drawn 0H through the bottom passage.

In vorder to give a' particularly intensive heating to the top heating iue sections 44, it is advisable to provide'guide walls 50 in the continuation of the passages 45. By means of these guide walls, the wastel gases in the top heating flue 44 are causedto pass along the walls 19 vfor a longer time.

In order to set the dampers which are arranged in the upper heating ilues 44, openings 51 are provided in the roof of the furnace' as usual, these being capable of being closed by means of removable closure plugs 52. 2f Instead of the upper heating passages beingheated by a horizontal partition wall being provided for this purpose in the heating fines, it is also possible according to the invention, to bring out a graded heating ofthe reduction retorts 6 by the thickness of the walls 19 being increased in the top portion of these retorts.

I claim:

1. A furnace battery .for the recovery of zinc from lead-bearing zinc ore admixed with carbon, comprising vertical retortsfor distilling the zinc ore and carbon mixture, heating walls forming the sides of the retorts and com rising upper and lower sections of heating ues provided with inlet and outlet openings for gas and air or waste gases, means whereby the walls of the retorts are brought to a lower temperature in their upper section v than in their lower section, a gas offtake for each retort for the gases and vapours produced during the distilling of the zinc ore, the said oftakes being arranged below the tops of the retorts and on a level with th upner section of the Aheatingr fines.

2. A furnace battery `for the recovery of zinc from lead-bearing zinc ores, comprising vertical retorts for distilling the zinc ore and carbon mixture, heating walls forming the sides of the retorts and comprising heating ues provided with inlet and outlet openings for gas and air or waste gases, means whereby the upper sections of the heating Walls of the retorts are brought to such a temperature that the zinc ore and carbon mixture in the upper portion of the retort is brought to a temperature of about 950 degrees, means whereby the lower section of the heating walls of the retort are brought to such a' temperature that the zinc ore and carbon mixture in the lower portion of the heating walls comprising vertical heating' lines forming the sides of the retorts, the

said heating fiues being provided with inlet and outlet openings for gas and air or waste gases, a horizontal flue arranged in the heating {iues to provide a less highly heated upper portion in the heating fines and a more lfighly heated lower portion in theh'eating ues.

4. A furnace battery for the recovery of zinc from lead-'bearing zinc ores admixed with carbon, comprising vertical retorts fordistilling the'zinc o re and carbon mixture, heating `walls comprising vertical heating fines forming sides of the retorts,'the said heating fines being provided below with inlet and outlet openings for gas 'and air or waste gases, a horizontal partition wall arranged in the vheating {iues and adapted to form the boundary between an upper less highly heated section and a lower more highly heated section in the heating fines, gas and air delivery conduits arranged in the said partition wall, inlet and outlet openings for gas and air or. waste gases provided at the under side of the partition wall, and vertical passages Aarranged in relation to said partition wall, whereby the bottom and the top section of the heating iluesv are connected together.

5. furnace battery for the recovery of zincl from lead-bearing zinc ores admixed with carbon, comprising vertical retorts for distilling zinc ore and carbon mixture, heating walls comprising vertical heating flues formingthe sides of the retorts, the said heating flues being provided below with inlet and outlet openings for gas and air or waste gases, a horizontal partition Wall in the heating fines, arranged to form the boundary be-4 tween an upper less highly heated flue section and a lower more greatly heated flue section in said heating wall, gas and air delivery conduits arranged in the said partition wall-and porting into the upper section of the heating flue, inlet and outlet openings for gas and air or waste gases porting from said partition wall-into the lower section of said heating lines, vertical passages arranged in relation to the said partition wall, whereby the lower and upper sections of the heatinglues are communicably connected together, danipers for the vertical passages connecting the upper and lower heating line sections, the

Lacasse heating Hues-being provided at the bottomwith inlet andoutlet openings for gas and air or waste gases, a horizontal partition wall in the heating Hues forming the limit bei tween an upper less highly heated Hue section and a lowermore greatly heated Hue section' in said heating walls,'inlet and outlet openings for gas and air or waste gases arranged at both the upper and lower sides of the said partition walls, soarranged that the upper and lower heating Hue sections are each heated by separate means.

7. A lfurnace battery for the recovery ,of

zinc from lead-bearing zinc ores admixed with carbon comprising vertical retorts vfor distilling the zinc ore and carbon mixture, heating walls comprising vertical heating Hues forming the sides of the retorts, the 'said heating Hues being provided at the bottom with inlet and outlet openings for lgas and air or waste gases, a horizontal partition wall in the heating Hues forming the limit between an upper less hi hly heated Hue section and a lower more .highly heated Hue section in said heating walls, gas and air delivery passages arranged in the said partition wall, inlet and outlet openings for gas and air or waste gases arranged at both the upper and lower sides of the said partition wall, so arranged that the upper and lower heating Hue sections are each'heated by separate'means,

passages arranged in relation to said partition wall communicably connecting the upper and lower heating Hue sections, the said passages being adapted to draw the waste gases from the -upper heating Hue section into the lower heating HueA section, and regenerators cannected with said air or waste gas passages and openings.

so that the connecting conduits communicate therewith at the upper ends of the upper Hue sections.

In testimony whereof I aHiX my s1 ature.

CONRAD H N.

8. A furnace battery for the recovery of zinc from lead-bearing zinc ores admixed wlth carbon, comprlslng vertical retorts for dlstllllng the Zlnc ore and carbon mixture,

heating walls com prising vertical heating Huesforming the sides of the retorts, a horizontal partition wall in the heating Hues and forming upper and lower Hue sections, vertical conduits, whereby the upper and lower' Hue sections are communicably connected together, the said connecting conduits entering into the upper heating Hue sectionsdirectly alongside the portion of the walls-facing the retort, guiding walls arranged on the horizontal partition wall and forming an extension of the vertical connecting conduits, thev said guiding walls terminating below the upper end of the upper heating Hue sections 

